Current or voltage regulator



Feb. 2s, 1939.

l. woLFF 2,149,080

CURRENT 0R VOL'l-AGE REGULATOR Filed NOV. 28, 1956 2 Sheets-Sheet l Snnenfor G ttomcg Feb. 28, 1939. l. woLFF Y CURRENT 0R VOLTAGE REGULATOR 2 Sheets-Sheet 2 Filed Nov. 28, 193e n@ Nmlx :inventor ff Gtforneg Patented Feb. 1939 UNITED ,STATES PATENT OFFICE Irving Wolff, Merchantville, N. J., assignor to Radio Corporation of America, a corporation o! Delaware Application November 28, 1936, Serial No. 113,184

11 Claims.

My invention relates to the regulation of current or voltage in a load circuitI as a function of thermionic emission and, more particularly, to means for maintaining constant current or constant voltage by deriving a regulating voltage which depends upon electronic emission in a vacuum tube.

I am aware of the use of numerous types of current or voltage regulators which employ vacuum tubes as amplifiers for the regulating means. In general, such devices depend upon current or potential differences in the load circuit. I propose to greatly increase the sensitivity' of a regulator by regulating the current as a function of thermionic emission. The substantial increase in regulation which I obtain is due to the fact that the proportional change of emission currents is about twenty to sixty times as great as the current'change in the cathode which produces the emission, depending upon the type of cathode and cathode temperature. It should be understood that my invention may be applied to regulation of current in a resistive load, an electron emissive load, the regulation oi' magnetizing current, and the like.

It is well known to those skilled in the art that ultra high frequency tubes have operating characteristics which may be very erratic. One oi the principal sources of variability is the filament emission of a microwave oscillator. One reason for such variation is due not only to variations in lament current but to filament bombardment. lt has been proposed that suitable means be employed to maintain constant lament current. l have found that constant filament current is not a complete solution of the problem.

I propose, as a principal object of my invention, means for maintaining constant current in a load circuit by means of a regulating voltage derived from a thermionic emission current which is dependent upon the iiow of current through the load circuit.

Another object of my invention is to maintain a constant voltage across a load circuit by means of a regulating voltage derived from a thermionic emission current which is dependent upon the current flowing through the load circuit` Another object of my invention is to provide means for maintaining constant emission from the cathode in a thermionic tube.

Another abject is to provide means for controlling thsemission in one tube by means of regulating currents which are derived from the emission currents in an auxiliary tube.

(Cl. Z50-27) Another object is to provide means for regulating a high frequency oscillatory current, which is used to heat the cathode of an ultra high frequency thermionic tube, by a controlling potential derived from the emission currents of the ultra high frequency tube.

A still further object is to provide means for maintaining a constant emission in a thermionic tube by energizing the cathode of the tube from a source of regulated high frequency oscillatory current.

An additional object is to provide means for protecting the catode of a thermionic tube in the event that failure develops in the regulation of the cathode heating control means.

My invention may be best understood by referring to the accompanying drawings, in which- Fig. 1 is a schematic circuit diagram of one embodiment of my invention,

Fig. 2 is a modiiication of the circuit diagram of Fig. l, in which a thermionic tube is used as a regulator,

Fig. 3 is a circuit diagram of an embodiment of my invention which includes direct current amplifiers and a converter which is regulated to maintain constant emission in an ultra high frequency tube, and

Fig. 4 is a modification which may be applied to the circuit of Fig. 3 and which employs an auxiliary tube.

Referring to Fig. l, a source of current l is connected to a load circuit 3, which is in turn serially connected to a regulator 5. The regulator E is connected to the cathode tl of a vacuum tube 9. The cathode 'l is connected by a lead il) to the source of current i. The vacuum tube Q includes an anode il, which is connected to the positive terminal of the anode battery it. The return to the cathode l from the negative terminal of the anode battery is made by means of a lead l5 through the regulator. 5.

'I'he operation of Fig. 1 is as follows: The vacuum tube 9 is adjusted to operate below the point of emission saturation, i. e., on the sloping portion of the characteristic cathode currentanode current curve. If the lsource of current varies, the current flowing through the cathode l will likewise vary. The currents emitted from the cathode will have a proportional change about twenty or more times as great as the cathode current variation producing the change. This change in emissive current is applied to the regulator to thereby increase or decrease the impedance of the regulator which regulates the current flow' in the load circuit. If the load is otthexesistivetypesndmalntainsaoonstant resistance. then the current through resistance may be maintained constant, and hence the voltle drop across the resistance will be constant. Inthlsmannenthecircuit oi'FIg. lmaybeused to regulate either the current or the voltage.

In Fig. 2, a simple form of regulator is substituted for the schematic illustration ln Fig. 1. Referring to Fig. 2. a source of current I1 is connected to a load circuit I9, which in turn is connected to the anode 2| of a thermionic tube 23. 'Ihe cathode 25 oi' this tube is connected to the cathode 21 oi a vacuum tube 29. The cathode circuit is completed by a lead 3|, which returns to the current source. The vacuum tube 29 has an anode 33 which is connected to the positive terminal of the anode battery 35. The negative terminal of the anode battery is connected to a resistor 31 which terminates in the lead 3|. A control grid 39, which is included within the thermionic tube 2,3, is connected to a slider 3|, which is adjustably connected to the resistor 31.

The operation oi' the circuit oi' Fig. 2 is essentially as follows: When the cathode of the thermionic tube 23 is suitably heated, currents will ilow from the source of current I1 through the lead 3|, through the cathode 21 of the vacuum tube 29, from the cathode 25 to the anode of the regulator tube 23, through the load circuit and back to the source I1. Since the vacuum tube 29 is adiusted, as previously described, to operate on the sloping portion oi the emission curve, any variation in current through the cathode 21 will change the emission currents and thereby vary the current flowing through the resistor 31. The variation in current through the resistor 31 will cause potential changes which are impressed on the grid 39. These potential changes will vary the impedance of the regulator tube 23 to thereby neutralize or compensate for the changes in current.

More specincally, if the current increases, the potential of the gird 39 will become more negative and thereby increase the impedance of the regulator tube, which in turn decreases the current flow. Conversely, if the current through the cathode 21 decreases, the emission currents decrease and the voltage drop applied to the grid 39 becomes less negative or more positive. A more positive potential applied to the grid 39 tends to decrease the impedance of the regulator tube and thereby increase the ilow of current and compensate for the diminishing current.

Referring to Fig. 3, a source of electric current is represented by the terminals IOI, |03. The upper or positive terminal is connected to the anode of a thermionic tube |05. The cathode of this tube is connected, through serially arranged resistors |01, |09, III, to the negative terminal |03. The three resistors |01, |09, are shunted by a serial array, comprising, in the order named, two resistors ||3, ||5, the anode-cathode path of a thermionic tube I I1, which is a direct current amplier, and a gaseous discharge tube I9. The grid |20 oi' the iirst mentioned thermionic tube is connected-to a point between the two resistors ||3, |5. 'Ihe screen grid I2| of the direct current amplifier tube ||1 is connected to the junction of resistors |01, |09. The control grid |23 of tube ||1 is adjustably connected to resistor |09.

Briefly, the operation of the above described circuit is to maintain a constant voltage across the three resistors |01, |09, III, to prevent excesammo sive voltages from being applied to the cathode oftheultra highirequency tubewhichistobe regulated. It the voltage across the resistors |01, |00, III rises, the potential of control gridl becomes more negative or less positive, thereby increasing the impedance of the tube |05. The tube |05, being serially arranged with respect to the source |0l, |03 andthe resistors |01, |00, III, will. when its anode-cathode impedance increases, decrease the voltage drop across the resistors |01, |00. III. Likewise, when the voltage across these resistors drops, the grid 20 becomes more positive and thereby decreases the anode-cathode impedance of tube |05 and increases the voltage across the resistors |01, |09, Thus the volt age is regulated.

'I'he three resistors |01, |09, III may be considered as the source of a constant voltage. This source is connected as follows: The upper terminal of resistor |01 is connected through a switch and contact |20 to the anode of a thermionic tube |21. The cathode of this tube |21 is connected to four serially connected resistors |29, |3I, |33, |35, which terminate in the lead |31 connected to resistor and terminal |03. Two, |29, |3|, of the four resistors are shunted by a serially connected array comprising resistor |39 and the anode-cathode path of a direct current amplifier tube 0 'I'he screen grid of the ampliiler tube III is connected to the junction of resistors |29, 3|. 'I'he control grid |03 of the iirst direct current amplifier tube Ill is connected to the anode I of a second direct current ampliner which is connected as follows: Anode I of tube |45 is connected, through resistor |01, to the upper terminal of resistor |29. The cathode of tube |55 is connected through a resistor I I9 to a slider on a resistor 5| which is connected to the lower terminal of resistor and to the cathode of the magnetron |53. The screen grid of tube is connected to the junction of resistors |33, |35. The control grid of tube |45 is adjustably connected to the fourth resistor |35. 'I'he four resistors |29, |3I, |33, |35 are shunted by a capacitor |55.

An oscillator |51 is connected as follows: A thermionic tube |59 is arranged with its cathode connected to the lead |31. The anode is connected through a resonant circuit ISI to the upper, or positive, terminal oi resistor |29. The grid is connected through a grid-leak resistor |63 and grid capacitor to an inductor |81, which is mutually coupled to the resonant circuit IBI. This oscillator generates a current preferably of superaudible frequency; e. g., 20 kilocycles per second. This high frequency current is induced in the tertiary winding |59 which is coupled to the resonant circuit 0|.

'I'he tertiary winding |59 is connected to the cathode |1| ofthe magnetron I 53. The magnetron |53. The magnetron circuit includes split anodes |13, |15, end plates |11, and the cathode I1I, which are mounted within an evacuated envelope I 19. The anodes |13, |15 are connected to a transmission line I 0| which terminates in an antenna |03. 'The mid-point of a bridging member |05, which is adjustably mounted on the transmission line, is connected to the positive terminal of a B voltage source |01. The end plates |11 are also connected to the B voltage source. The cathode return is made by the lead |88, which connects the cathode |1| to the resistor |5|, which is in turn connected to the negative terminal of the B voltage source |01.

Neglecting for the moment the characteristics of the constant voltage source, the theory ot operation of the circuit may be explained as follows: The magnetron cathode |1| is heated by high frequency currents from the oscillator |51. The emission from the magnetron cathode |1| to the anodes |13, |15 and end plates |11, establishes an anode current which flows through the resistor |5| and back to the cathode through lead |58. While the emission currents are steady, no change in voltage is established across the resistor |5| through which the magnetron emission current ilows and no regulation is obtained.

If, however, the emission current decreases, less current flows through the resistor |5|, and the cathode of tube becomes more negative with respect to its control grid |45. With a more positive control control grid (i. e., more negative cathode), more current will flow in this tube |45, and therefore its anode |44 will be less positive.

'Since the control grid of tube |4| is connected to the anode |44 of tube |45, the control grid |43 will likewise be less positive. A less positive control grid |43 will decrease the current in the anode circuit of tube |4|,- and therefore the anode will become more positive. The control grid of tube |21, being connected to the anode of tube |4|, will become more positive, and therefore will decrease the impedance of tube |21.

The decrease in impedance of tube |21 will decrease the voltage drop in this tube, and therefore raise the potential of the anode of the oscillator tube |59. This' increase in potential will increase the high frequency oscillatory output currents of the oscillator |51, whereby the high frequency oscillatory current in the cathode |1| will be increased to increase its emission. Thus, a decrease in emission is compensated or neutralized by increasing the cathode emission. In a reverse manner, an increase in the magnetron emission current will be neutralized by a decrease in the high frequency oscillator |51 output.

Thus, the emission from the cathode of the magnetron |53 is maintained substantially constant by increasing or decreasing the cathode current, not to maintain constant cathode current, but constant cathode emission. This method of control is muchmore sensitive than attempting to maintain a constant cathode heating current. I have determined that control by emission regulation is not only about twenty or more times more sensitive than control of the heating current, but also that the latter method does not provide means for compensating for cathode bombardment, which is very important in ultra high frequency oscillators of either positive grid or magnetron type.

In some instances, I have found that the cathode emission is too low to provide a suitable type of control. In such cases, an auxiliary emitter may be arranged with-its cathode heater serially connected to the heater of the tube to be controlled. This arrangement is indicated in Fig. 4, in which the circuit has been limited to the essential parts. The magnetron |9| has a cathode |93, which is serially connected to the cathode |95 of an auxiliary diode |91. The serially connected cathodes are connected to the tertiary winding of the high frequency oscillator illustrated in Fig. 3. The an'ode |99 of the auxiliary tube |91 is connected to the positive terminal of a B battery 20|. The negative terminal of the B battery is connected through a resistor 203 to the junction of the cathodes |93, |95. The resistor 203 corresponds to the resistor |5| of Fig. 3. The description of the remaining connections is similar to that of Fig. 3, and will, therefore, not be repeated.

In the present circuit, Fig. 4, the emission in tube lil is not suflicient to provide suitable regulation. The emission in the auxiliary tube ls determined by the characteristics of the tube |51 and the anode battery 20| voltage. The emission of the auxiliary tube is regulated to maintain constant emission currents, and' since the cathode of the main tube |9| and the auxiliary tube |91 are in series, the emission of the former, |9|, will be regulated by the latter, |91. In the present application, the effects of the cathode bombardment in the main tube |9| will not be controlled, but fortunately, with low emission cathode bombardment may generally be neglected. 'Ihe cathode emission of the main tube is much more closely regulated by the control of emission in the auxiliary tube than it would be if the regulator were of the ordinary constant cathode current type.

While the foregoing description has been limited to magnetron tubes, it should be understood that the invention may be applied to positive grid oscillators, ultra high frequency tubes, 0r any thermionic tube. Likewise, while a constant vol'age source is shown, such source is by way of illustration. Its function is to limit the maximum voltage on the oscillator |53 to prevent burn-out of the cathode I1 if the emissive regulaion should fail. In some instances it may be desirable to omit the emission control during adjustment. This may be effected by connecting switch |25 to the adjustable resistor |24. The frequency of the high frequency oscillator |51 is described as above audible frequencies, but it is not my intention to thereby limit the frequency to any particular value.

The direct current amplifiers of Fig. 3 may be applied to amplify the regulating voltage of the systems described by Figs. 1 and 2. Likewise, the current source of Figs. 1 and 2 may be applied to a converter or generator as shown in Fig. 3. In a similar manner, the constant voltage source oi' Figs. 1 and 2 may be substituted for the constant voltage regulator which is applied to the source |0| of Fig. 3. Numerous other modiiications within the scope of my invention will occur to those skilled in the art.

I claim as my invention:

1. In an apparatus of the character described, a source of current, a load circuit, a variable impedance device, means for emitting thermionic currents, means for serially connecting said source, load circuit, variable impedance device and emitting means, means for deriving a regulating potential from said thermionic currents,

and means for applying said regulating potential to said variable impedance device whereby its impedance is varied to regulate the current flowing in said load circuit.

2. In an apparatus for regulating current, a source of current, a load network, a three-element vacuumtube including grid, cathode and anode electrodes, a two-element vacuum tube including cathode and anode electrodes, means for passing currents from said source through said load network, the cathode-anode path of said three-element tube, and the cathode of said two-element tube, means including a resistor for passing thermionic currents from the cathode to the anode of said two-element tube whereby a regulating potential is developed across at least a portion of said resistor, and means for impressing said regulating potential on the grid electrode of said three-element tube whereby the impedance of said three-element tube is varied to thereby regulate the ilow of current through said load network.

3. The method oi controlling cathode emission currents which comprises generating an oscillatory current, applying said oscillatory current to heat said cathode to an emissive temperature. deriving a regulating voltage from said emission, applying said regulating voltage to control the said applied oscillatory heating currents and thereby control the emission from said cathode.

4. The method of controlling cathode emission by means of an auxiliary emissive source which comprises generating an oscillatory current, applying said oscillatory current to said cathode and said auxiliary emissive source to heat the same to emissive temperatures, deriving a regulating voltage from said auxiliary emission, applying said regulating voltage to control the oscillatory heating currents applied to said cathode and auxiliary emissive source.

5. The method of controlling cathode emission which comprises generating an oscillatory current from a source of current including a variable impedance, heating said cathode by said oscillatory current whereby emissive currents are established, deriving a controlling voltage from said emissive currents, applying said controlling voltage to said variable impedance, regulating the value of said-variable impedance by said applied controlling voltage whereby the voltage derived from said source and the amplitude of said oscillatory currents are varied to neutralize any changes in said emissive currents.

6. The method described in claim 5 plus the additional step of regulating the voltage of the source prior to its application tosaid variable impedance.

7. The method described in claim 5 plus the additional step of amplifying said controlling voltage before applying said controlling voltage to said variable impedance.

8. In a device of the character described. the

combination of a source of current. a variable impedance, means for converting the currents from said source into oscillatory currents, means for serially connecting said source, said variable impedance and said current converting means, a vacuum tube including cathode and anode electrodes, means for applying said oscillatory currents to said cathode whereby said cathode is heated to emit electrons, means for deriving a controlling potential from said emitted electrons, and means for applying said controlling potential to said variable impedance whereby the amplitude of said oscillatory currents is regulated.

9. In a device of the character described, the combination of a source of current, a variable impedance, 4means for converting said source currents into oscillatory currents, means for serially connecting said source, said variable impedance and said current converting means, a vacuum tube including cathode and anode electrodes, means for applyingI said oscillatoryv currents to said cathode whereby emission currents are established between said electrodes, means for deriving a controlling potential from said emission currents, means for amplifying said controlling potential, and means for applying said ampliiled potential to vary said impedance whereby the potential o1.' the currents from said source is varied and .the amplitude of the converted currents regulated to maintain substantially-constant emission currents.

10. In a device o1' the character of claim 8, separate means for maintaining the potential of said source substantially constant to thereby limit the potential applied to said current convacuum tube.

IRVING WOLFF. 

